Comparison of Thermal Resistance Between Solid and Liquid Silicone Rubber
Abstract
Silicone rubber is widely used in industries requiring high thermal stability, such as automotive, medical, and electronics. Both solid silicone rubber (HTV – High-Temperature Vulcanizing) and liquid silicone rubber (LSR – Liquid Silicone Rubber) exhibit excellent heat resistance, but their performance varies due to differences in molecular structure and curing mechanisms. This article compares their thermal resistance, influencing factors, and typical applications.
1. Introduction
Silicone rubber is a synthetic elastomer known for its flexibility, chemical inertness, and thermal stability. Solid silicone (HTV) and liquid silicone (LSR) are two primary forms, differing in viscosity, curing methods, and mechanical properties. While both can withstand high temperatures, their maximum service temperatures and degradation behaviors differ.
2. Thermal Resistance of Solid Silicone Rubber (HTV)
Temperature Range: Typically withstands -60°C to 250°C continuously, with short-term exposure up to 300°C.
Key Factors:
Filler Materials (e.g., silica, alumina trihydrate) enhance heat resistance.
Crosslinking Density: Higher crosslinking improves thermal stability.
Degradation Mechanism:
Above 250°C, oxidative degradation occurs, leading to hardening and loss of elasticity.
Prolonged exposure to >300°C causes backbone scission (Si-O bond breakdown).
3. Thermal Resistance of Liquid Silicone Rubber (LSR)
Temperature Range: Generally operates between -50°C to 200°C, with short-term tolerance up to 250°C.
Key Factors:
Platinum-Catalyzed Cure: Provides uniform crosslinking but may degrade faster under extreme heat than peroxide-cured HTV.
Additives: Flame retardants and thermal stabilizers can extend upper limits.
Degradation Mechanism:
At >200°C, LSR may soften or lose mechanical strength faster than HTV due to lower molecular weight.
4. Comparative Analysis
| Property | Solid Silicone (HTV) | Liquid Silicone (LSR) |
|---|---|---|
| Continuous Use Temp | -60°C to 250°C | -50°C to 200°C |
| Peak Short-Term Temp | Up to 300°C | Up to 250°C |
| Thermal Aging | Slower degradation | Faster softening at high heat |
| Curing Method | Peroxide/heat vulcanized | Platinum-catalyzed (softer cure) |
5. Applications Based on Thermal Needs
Solid Silicone (HTV):
Automotive gaskets (engine components)
Industrial seals (high-heat environments)
Insulation for electrical cables
Liquid Silicone (LSR):
Medical devices (sterilization at ~200°C)
Baby bottle nipples (food-safe, moderate heat)
Consumer electronics (flexible seals)
6. Conclusion
While both solid and liquid silicone rubbers exhibit strong thermal resistance, HTV generally outperforms LSR in extreme heat (>200°C) due to its higher crosslinking density and filler reinforcement. LSR is preferable for precision molding and medical applications where moderate heat resistance suffices. Material selection should consider temperature exposure, mechanical demands, and processing requirements.